OpenNTPD is a FREE, easy to use implementation of the
Network Time Protocol.
It provides the ability to sync the local clock to remote NTP servers
and can act as NTP server itself, redistributing the local clock.

OpenNTPD was primarily developed by Henning Brauer as
part of the OpenBSD Project
and gets released as a base component of OpenBSD every six months.

The portable version, maintained by Brent Cook, is available
via periodic tarball releases. Contributions are welcome to both the
OpenNTPD core and the portable build framework.

The software is freely usable and re-usable by everyone under
a BSD license.
The OpenBSD project sells
CDs, T-shirts and posters.
Sales of these items help to fund development.